Semiconductor devices are commonly found in modern electronic products. Semiconductor devices vary in the number and density of electrical components. Discrete semiconductor devices generally contain one type of electrical component, for example, light emitting diode (LED), small signal transistor, resistor, capacitor, inductor, and power metal oxide semiconductor field effect transistor (MOSFET). Integrated semiconductor devices typically contain hundreds to millions of electrical components. Examples of integrated semiconductor devices include microcontrollers, microprocessors, charged-coupled devices (CCDs), solar cells, and digital micro-mirror devices (DMDs).
Semiconductor devices perform a wide range of functions such as signal processing, high-speed calculations, transmitting and receiving electromagnetic signals, controlling electronic devices, transforming sunlight to electricity, and creating visual projections for television displays. Semiconductor devices are found in the fields of entertainment, communications, power conversion, networks, computers, and consumer products. Semiconductor devices are also found in military applications, aviation, automotive, industrial controllers, and office equipment.
Semiconductor devices exploit the electrical properties of semiconductor materials. The atomic structure of semiconductor material allows its electrical conductivity to be manipulated by the application of an electric field or base current or through the process of doping. Doping introduces impurities into the semiconductor material to manipulate and control the conductivity of the semiconductor device.
A semiconductor device contains active and passive electrical structures. Active structures, including bipolar and field effect transistors, control the flow of electrical current. By varying levels of doping and application of an electric field or base current, the transistor either promotes or restricts the flow of electrical current. Passive structures, including resistors, capacitors, and inductors, create a relationship between voltage and current necessary to perform a variety of electrical functions. The passive and active structures are electrically connected to form circuits, which enable the semiconductor device to perform high-speed calculations and other useful functions.
Semiconductor devices are generally manufactured using two complex manufacturing processes, that is, front-end manufacturing, and back-end manufacturing, each involving potentially hundreds of steps. Front-end manufacturing involves the formation of a plurality of semiconductor die on the surface of a semiconductor wafer. Each semiconductor die is typically identical and contains circuits formed by electrically connecting active and passive components. Back-end manufacturing involves singulating individual semiconductor die from the finished wafer and packaging the semiconductor die to provide structural support and environmental isolation. The term “semiconductor die” as used herein refers to both the singular and plural form of the words, and accordingly can refer to both a single semiconductor device and multiple semiconductor devices.
One goal of semiconductor manufacturing is to produce smaller semiconductor devices. Smaller devices typically consume less power, have higher performance, and can be produced more efficiently. In addition, smaller semiconductor devices have a smaller footprint, which is desirable for smaller end products. A smaller semiconductor die size can be achieved by improvements in the front-end process resulting in semiconductor die with smaller, higher density active and passive components. Back-end processes may result in semiconductor device packages with a smaller footprint by improvements in electrical interconnection and packaging materials.
Back-end processing of semiconductor die includes a number of surface mount technologies (SMT) that are used to connect semiconductor die or integrated circuits to surfaces of substrates and printed circuit boards (PCBs) without the use of through holes in the PCBs. Quad Flat Packages (QFP) use SMT that includes leads that extend from each of the four sides of the package, sometimes referred to as “gull wing leads.” QFP leads provide electrical Input/Output (I/O) interconnection between the semiconductor die within the package and the PCB or substrate to which the QFP is mounted. Other SMT packages are made without leads and are commonly referred to as flat no lead packages. Examples of flat no lead packages are Quad-flat no leads packages (QFNs) and dual-flat no lead (DFN) packages. QFN packages conventionally include a semiconductor die connected by wirebonds to a leadframe that is used for package I/O interconnection.
One approach to back-end processing that more efficiently produces packaged semiconductor devices is the use of panelized packaging, in which a number of semiconductor die are formed into a panel and processed simultaneously at a level of a reconstituted wafer or panel. One form of panelized packaging used to package semiconductor die is fan-out wafer level packaging (FOWLP). FOWLPs involve placing multiple semiconductor die “face down” or with an active surface of the semiconductor die oriented toward a temporary carrier or substrate, such as a temporary tape carrier. FOWLPs can also be fabricated by placing the semiconductor die “face up” on a temporary or permanent carrier. The semiconductor die and substrate or carrier is overmolded with an encapsulant, such as an epoxy molding compound, using, for example, a compression molding process. After molding, the carrier tape is removed to expose the active surface or the back surface of the multiple semiconductor die formed together as a reconstituted wafer. Subsequently, a wafer level chip scale package (WLCSP) build-up interconnect structure is formed on top of the reconstituted wafer. Conductive bumps can then formed over the build-up interconnect structure as a ball grid array (BGA), which is attached to the reconstituted wafer. After formation of the BGA, the reconstituted wafer is singulated to form individual semiconductor devices or BGA packages that can provide more numerous package I/O connections than conventional packages.